I’m making a new bench and I have glued up the base – blind mortises. Now I wonder if I should drill all the way through legs and tenons and add a pin.
Will it add strength to the joints ? or is it to late when the tenon-hole cannot be offset to give the pull effect.
Thanks, Ole
…. I Love the smell of sawdust in the morning….
Replies
I'd leave it alone at this point, the joints will probably hold up just fine without adding pins. If the joints don't hold, then you can take the bench apart, clean up the joints for regluing, and properly drill for offset holes before you reassemble the base.
John W.
Ole,
I think of pinning a mortise and tenon joint as a sort of insurance against the joint breaking loose. I'm not sure it adds any strength, just a mechanical means, in addition to the chemical glue bond, for holding the joint together. The pins look good, too, I think.
If the glue joint should fail, the pins may hold things tightly for a while, but the racking forces applied to the base of a workbench in use would eventually cause the pins to fail as well.
Standard procedure in one of the shops where I worked was to clamp the joint, and then drill and pin it. Clamps could then be removed and used on the next piece, without waiting for the glue to set. I wonder if this isn't one reason that old pieces were pinned as well.
I'm not a fan of draw-bore (offset holes) pinning. Many of the draw-bore pins I've seen in repair work were either cracked or sheared off inside the joint, or had broken the tenon out through its end. The only practical use I can think of to draw-bore a joint is in house or barn framing, where there isn't any glue to hold the joints tightly.
Good luck on your bench project. Looks like a good one!
Cheers,
Ray
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